1. Field of the Invention
The present invention relates to a piezoelectric actuator having a piezoelectric element that deforms in response to a voltage applied thereto and thereby displaces an object supported by the piezoelectric actuator and to a head suspension employing the piezoelectric actuator.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing, and for use with such devices, needs for micro-actuators capable of conducting positioning control for very small distances are increasing. The micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink-jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
The magnetic disk drives increase storage capacity by increasing the number of tracks per inch (TPI), i.e., by narrowing the width of each track on a magnetic disk.
Large-capacity magnetic disk drives, therefore, need an actuator capable of precisely positioning the magnetic head within a minute range across tracks.
To meet the need, Japanese Unexamined Patent Application Publication No. 2002-184140 discloses a head suspension employing a dual actuator system. The dual actuator system uses a piezoelectric element in addition to a usual voice coil motor that drives a carriage to which the head suspension is attached. The piezoelectric element is arranged between a base plate and a load beam of the head suspension, to minutely move a magnetic head attached to a front end of the load beam.
According to this related art, the voice coil motor turns the head suspension through the carriage, and in addition, the piezoelectric element deforms in proportion to a voltage applied thereto, to minutely move the magnetic head at the front end of the load beam in a sway direction (a width direction of the load beam) relative to the base plate. The dual actuator system involving the voice coil motor and piezoelectric element is capable of precisely positioning the magnetic head to a target position on a magnetic disk.
The head suspension with the dual actuator system employs an actuator base for fitting the piezoelectric element to the head suspension.
The actuator base generally has an opening to accommodate the piezoelectric element and a receiver arranged at the opening and supporting the piezoelectric element. The piezoelectric element is set in the opening and a liquid adhesive is applied and solidified between the piezoelectric element and the receiver and inner circumference of the opening, thereby fixing the piezoelectric element to the actuator base.
When attaching the piezoelectric element to the actuator base, the piezoelectric element is positioned with respect to a thickness-direction center line in the opening of the actuator base. The receiver to receive the piezoelectric element at the opening is formed by laying a discrete receiver member on the actuator base. The receiver member is arranged outside the opening.
This configuration frequently creates small gaps in an overlapping area where the actuator base and receiver member are laid one on another. These gaps draw a liquid adhesive before solidification due to a capillary phenomenon.
If the liquid adhesive is made of a base adhesive and hardening particles, only the base adhesive will penetrate the gaps and the penetrated base adhesive will not solidify. Even if it solidifies, the adhesive in the overlapping area affects the dynamic characteristics such as resonance and windage characteristics of the head suspension.